Immunologic and clinical effects of antibody blockade of cytotoxic T lymphocyte-associated antigen 4 in previously vaccinated cancer patients

Abstract

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) functions as a negative regulator of endogenous and vaccine-induced antitumor immunity. The administration of fully human anti-CTLA-4 blocking monoclonal antibodies to advanced-cancer patients increases immune-mediated tumor destruction in some subjects. Nonetheless, patients that respond also frequently manifest serious inflammatory pathologies, raising the possibility that the therapeutic and toxic effects of CTLA-4 blockade might be linked. Here we show that periodic infusions of anti-CTLA-4 antibodies after vaccination with irradiated, autologous tumor cells engineered to secrete GM-CSF (GVAX) generate clinically meaningful antitumor immunity without grade 3 or 4 toxicity in a majority of metastatic melanoma patients. The application of this sequential immunotherapy to advanced ovarian carcinoma patients also revealed that tumor destruction and severe inflammatory pathology could be dissociated, although further refinements are required to increase clinical responses and to minimize toxicity in this population. The extent of therapy-induced tumor necrosis was linearly related to the natural logarithm of the ratio of intratumoral CD8(+) effector T cells to FoxP3(+) regulatory T cells (Tregs) in posttreatment biopsies. Together, these findings help clarify the immunologic and clinical effects of CTLA-4 antibody blockade in previously vaccinated patients and raise the possibility that selective targeting of antitumor Tregs may constitute a complementary strategy for combination therapy.

Fig. 1.

CTLA-4 antibody blockade triggers a partial breach of tolerance to normal skin. (Top Left) Perivascular infiltrates (H&E). (Magnification: ×20.) (Top Right) Interface dermatitis (H&E). (Magnification: ×40.) (Middle) CD3 and FoxP3⁺ (×20), and CD4 and CD8 (×40). (Bottom Left) Colloidal iron stain reveals mucin accumulation in the dermis. (Magnification: ×20.) (Bottom Right) Colloidal iron stain, normal skin. (Magnification: ×20.)

Fig. 2.

CTLA-4 antibody blockade precipitates a sarcoidosis-like pathology. (Top Left) Involved hilar lymph node (H&E). (Magnification: ×4.) (Top Right) Noncaseating granulomas (H&E). (Magnification: ×10.) Immunostains: S100, CD68, CD3, and FoxP3 (Magnification: ×20).

Fig. 3.

CTLA-4 antibody blockade evokes durable objective responses of metastatic melanoma with minimal toxicities. Serial thoracic CT scans document a transient increase in size of a pulmonary nodule (arrows) and pleural-based disease (brackets) followed by marked regression of the involved sites.

Fig. 4.

The ratio of tumor-infiltrating CD8⁺ T cells to FoxP3⁺ Tregs after Ipilumimab infusion is tightly correlated with the extent of tumor necrosis. (A Upper) Minimal necrosis of melanoma metastasis. (Lower) Extensive necrosis of melanoma metastasis. (Magnification: H&E, ×4; CD8, ×20; FoxP3, ×40.) (B) Numbers of intratumoral FoxP3⁺ Tregs and CD8⁺ T cells versus tumor necrosis.

Fig. 5.

CTLA-4 antibody blockade accomplishes the durable regression of advanced ovarian carcinoma in the absence of significant toxicity. (A) CA-125 levels as a function of therapy. Small upward arrows indicate GVAX; downward arrows denote Ipilumimab infusions. (B) Arrow indicates a large hepatic metastasis that underwent marked regression. (C) MDX-010 augmented IgG antibodies to NY-ESO-1.